Current-limiting device.



' v No. 696,055. Patented Mar. '25, I902.

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(Applicnion filed July 31, 1901.)

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dingy No. 696,055. Patented Man 25, 1902.

' S. L. G. KNOX.

CURRENT LIMITING DEVICE.

(Application filed July 31, 1901.) (No Modal.) 2 Sheets-Shoe! 2 Fig. 5

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Unrrsn STATES PATENT OFFICE.

SAMUEL L. G. KNOX, OF SCHENEC"ADY, NEW YORK, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NElV YORK.

DEVICE.

SPEGEFICEATION forming part of Letters Patent No. 696,055, dated March25, 1902.

Application filed July 31,1901, Serial No. 70,358. (No model.)

To cal], whom it 1mg]; concern:

Be it known that I, SAMUEL L. G. KNOX, acitizen of the United States,residing at Schenectady, county of Schenectady, State of New 5 York,have invented certain new and useful Improvements in Current-LimitingDevices, (Case No. 1,929,) of which the following is a specification.

This invention relates to the operation of to electric-motorcontrollers, and has for its obj cut the provision of improved means forpreventing such controllers from being turned on too rapidly.

I propose to furnish a member composed of :5 a pivoted arm and a shoeadapted to engage with an engaging surface provided for the purpose uponthe movable portion of the controller, an adjustable spring for normallyholding the shoe away from the engaging surface, and a coil connected inthe circuit which is to govern the operation of the device. If desired,the adjustment of the spring may be assisted or dispensed with by providing well-known means for adjusting the proportion of current in thecoil to that in the circuit to which it is connected. The shoe is somounted that when it is in contact with the engaging surface any effortto move the movable part in one direction will wedge 0 the surface andshoe together, thus effectually preventing movement in that direction;but effort to mov it in the opposite direction will reverse the wcdgingaction and the de vice will not obstruct its motion. The shoe 5 willcome in contact with the engaging surface whenever the current in thecoil rises to such value that the tension of the spring is overcome bythe magnetism induced through the shoe and engaging surface. When the 40current subsides, the spring will again become dominant and remove theshoe and surface from contact.

Having given an outline of my invention, 1 will now describe it indetail as applied to a hand-operated controller of the usual cylindricaltype, which I consider one of its best applications.

Referring to the drawings, Figure l is a front elevation of thecontroller with a portion of the cover at the bottom removed that myinvention may be seen. Fig. 2 is a sec tion of the controller at A B",Fig. 1, showing a plan view of my invention. Fig. 3 is a diagram ofconnections.

Referring to Fig. 1, CL is the cylinder or 35 movable portion, carryingcontacts 7; and rigidly connected to shaft S. The stationary contactsare not shown, as they would complicate the drawings without aiding inthe illustrationot' my invention. They are, however, showndiagrammatically in Fig. 3. XV is a wheel keyed to shaft S and furnishesan engaging surface upon its circumference for shoe 1). Flanges f serveas guides for shoe 1). H is a handle for imparting a rotary motion toshaft S, to which it is rigidly connect ed. Shaft S is supported bybearings 13 at the bottom and B" in the top of the controller case. BSis a handle for actuating a reversing-cylinder. This cylinder isconcealed beneath the controller-cover K and is not necessary to a fulland clear description of my invention.

Referring to Fig. 2, arm a is screwed to back of controller 0" andsupports coil C, through which circuit is made by leads Z. Arm a ispivoted to arm a, at p and at its other extremity carries the shoe Z).(Flange of wheel W is broken away to show shoe.) Springs tends to holdshoe Z) away from wheel N, and its tension can be adjusted by screwt andnut n. For best results in this construction screw t should be made ofbrass or other non-magnetizable material. Stop (Z is to prevent spring 5from drawing shoe b too far away from wheel V7.

Referring to Fig. 3, A is the armature of the motor; F, the iield. D isthe controller, shown diagrammatically, havingthe movable contactsappearing as developed on a plane surface and the stationary contacts 12 to 6 as small circles, according to the usual practice in diagrams ofsuch structures. R is the usual starting-resistance. C is the coil forenergizing the magnetic circuit through shoe 5 Z), and M and M theconductors of the supplycircuit.

The controller being in the off position, as shown, and it being desiredto start the motor, the handle H, Fig. 1, is turned to the right or inthe direction of the arrow, Fig. 2, so that (referring to Fig. 3) thelines 7 7 8 8 to 11 11 R, ari'nature of motor A, field of motor F toFurther movement of the conconductor M. troller operates to cut outresistance R in a well-known manner until, in the last position,

when line ll 11 is over the stationary contacts, the resistance is allcutout and the motor is in series with coil between conductors M and M.The resistance of coil 0 will ordinarily be so low as to have noappreciable As the controller is turned on the current passing etfectonthe operation of the motor.

throughthe coil 0 energizes a magnetic circuit, which may betraced asfollows, (see Figs. 2 and 1:) through arms a and a, shoeb, air-gap g,wheel W, shaft S,'bearings B and B, and controller-back r. The back 1 ofthe controller, the shaft 8, and bearings B and B are usuallyconstructed of iron, and this is the best material for my purpose. Thewheel motion.

W and arms a and a should also be constructed of iron or othermagnetizable material; but the shoe 1) should be made of brass or-othernon-magnetizable material for reasons as will appearlater. With theexception of air-gap g and shoe 1) we now have a circuit composedentirely of magnetizable material, which insures efficient utilizationof the magneto-motive force developed by coil 0 and also directs theinduction in the proper course-i. e., across air-gap g. The energizingof this circuit'by current in coil 0 tends to bring the shoe b incontact with the periphery of the wheel W, but ordinarily this isprevented by spring 8. If, however, the current reachesor exceeds acertain value, the tension of the spring is overcome and the shoe comesin contact with the wheel. The tendency then is for the shoe to adhereto the circumference of the wheel, so that any further efiort to turn onthe controller will but operate to wedge the wheel W, shoe 1), and arm abetween shaft S and pivot 19, and the greater the efiort put forth thetighter will the parts mentioned be wedged together, thus effectuallypreventing movement of the controller in this direction. If, however, itis desired to move the controller in the opposite direction or turn itoff, it is evident that the wedging action will be reversed, and therewill consequently be no opposition to such After the device describedhas operated to prevetfurther movement of the controller in a certaindirection it will remain in that condition until the current in coil 0(and that in the motor) has fallen to a certain value, when the spring 8will overcome the magnetic attraction between arm a and wheel W. Theshoe b will then be removed from contact with wheel W and the controllerfree to be turned farther on. It is a matter of general knowledge in theart that if a magnetic circuit composed entirely of magnetizablematerial is energized by means ofa currentflowing-in a coil which isinterlinked with it that thematerial will retain magnetism after-thecurrent will adhere stronglytogether. This efiect':

can be eliminated to-a large extent if a portion of the circuit becomposed of non-mag netizable material. I have thereforespech fiedthat'the shoe'b should be of brass or other non-.magnetizable material,so that it may be promptly removed from contact withwheel W when thecurrent falls' p I desire it to be understood tion is not limited to'theparticular construe- M .80 that myinvention which I have illustrated inthis applica I tion.

' which I have shown the magneticcircuit of For example, while in theoonstruction the coil which actuates the shoe is directed through theshoe and the engaging surface" it is evident that this'is not anecessary fea-' ture of my invention. claims I aim to cover allmodifications which embody the essence of my invention.

In the appended What I claim as new, and desire to secure 1 by LettersPatent of the United States, is

1. The combination in a current-controller of an engaging surface upon amovable member thereof, a shoe adapted to engage with said engagingsurface and a coil, the whole so arranged and constructed that themagnetic circuit of the coil is directed through said shoe and saidengaging surface and the said shoe so mounted that when it is in contactwith the said engaging surface, efiort to move the movable body in onedirection will wedge them together but effort in the opposite directionwill reverse such wedging action.

2. The combination in a current-controller of an engaging surface upon amovable member thereof, a pivoted arm, a shoe carried by said arm andadapted to engage with said engaging surface, a spring normally holdingsaid shoe away from said engaging surface, means for preventing thespring from drawing said shoe too far away from said surface, a coil,and means for adjusting the operation of the device to respond tocertain currents in said coil, the whole so arranged and constructedthat the magnetic circuit of the coil is directed through said shoe andsaid engaging surface and said shoe so mounted that when it is incontact with said engaging surface effort to move the movable body inone direction will wedge them together but effort in the oppositedirection will reverse such wedging action.

3. The combination of a current-controller, an engaging surface on amovable portion thereof, a pivoted arm, a shoe carried by said arm andadapted to engage with said engaging surface, a spring normally holdingsaid shoe away from said engaging surface,means for preventing thespring from drawing said shoe too far away from said engaging surface, acoil and means for adjusting the op eration of the'device to respond toany given current in the coil, the whole so arranged and constructedthat the magnetic circuit of the coil is directed through said shoe andsaid engaging surface and said shoe so mounted that when it is incontact with said engaging surface, effort to move the movable portionin one direction will wedge them together but effort in the oppositedirection will reverse such wedging action.

4. The combination of a cylindrical current-controller, a Wheel mountedon the cylinder-shaft, a pivoted arm, a shoe carried by said arm andadapted to engage with the periphery of said wheel, an adjustable springnormally holding said shoe away from said wheel, a stop for preventingthe spring from drawing said shoe too far away from said wheel and acoil connected in the circuit controlled by the controller, the whole soarranged and constructed that the magnetic circuit of the coil isdirected through said shoe and said whcchand said shoe so mounted thatwhen it is in contact with said Wheel, effort to turn on controller willwedge them together but effort to turn it off will reverse such wedgingaction.

5. The combination in a current-controller of an engaging surface upon amovable member thereof, a shoe adapted to engage with said engagingsurface and an electricallyactuated device tending to bring said shoe incontact with said engaging surface, the said shoe being so mounted thatwhen it is in contact with said engaging surface, effort to move themovable body in one direction will wedge them together, but effort inthe opposite direction will reverse such wedging action.

In witness whereof I have hereunto set my hand this 80th day of July,1901.

SAMUEL L. G. KNOX.

\Vitnesses:

BENJAMIN B. HULL, l\-'[ARGARET E. WooLLEv.

